6-Pyridylvinylpyridazine-3(2H)-one and the 4,5-dihydro compound have been described as having cardiotonic and/or antihypertensive activity in European Patent Application No. 81,906. 4,5-Dihydro-6-[2-[4-(1H-imidazol-1-yl)phenyl]ethenyl]-3 (2H)-pyridazinones are the subject of U.S. application Ser. No. 669,323 filed Nov. 9, 1984 now U.S. Pat. No. 4,599,332, which is equivalent to EP No. 84308465.8 filed Dec. 6, 1984. The present invention differs in that it does not include an imidazolyl substituent and, theretore, is not taught by EP No. 84308465.8 which additionally is not yet published.
Other pyridazinone type compounds are taught in the U.S. application Ser. No. 477,695 filed Mar. 22, 1983, and U.S. application Ser. No. 685,640 filed Dec. 24, 1984, and U.S. Pat. No. 4,353,905 issued Oct. 12, 1982. U.S. Pat. No. 4,353,905 includes an imidazolyl substituent but does not teach the alkenylene bridge of the present invention. None of the aoove references include a combination of pyridazinone substituents of the present invention.